Portable alarms for movable closures, such as doors and windows, are known in the prior art and some examples of the patented prior art are shown in U.S. Pat. Nos. 3,270,333; 3,378,830 and 3,878,539.
The general objective of this invention is to improve on the prior art pertaining to intrusion alarms for doors and the like by the provision of a device which is more sturdy and economical in construction and more reliable in operation. More particularly, the invention features a more powerful buzzer of the six volt type powered by four one and one-half volt batteries contained in a sturdy holder attached to the base or mounting plate of the alarm device. Ears or extensions on the battery holder project through apertures in the mounting plate and cooperate with companion extensions carried by an adjustable mounting bracket through which the device is suspended from the top edge of a door. A strong torsion spring on the hinge pintle which connects the suspension bracket and mounting plate assures reliable biasing of the device toward a fixed abutment and reliable operation of the alarm when the door or other closure is moved by an intruder.
Other features and advantages of the invention will become apparent during the course of following description.